1. Field of the Invention
The present invention relates generally to carbide and nitride composite materials, the manufacture of such composites, and their use in the glass making process.
2. Description of the Related Art
Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.
Carbides and nitrides are commonly used to form various articles that can withstand high temperature and stress without substantial deterioration. They are particularly suitable for applications in which oxidation at higher temperatures is not desirable, or in which abrasion resistance, thermal and electrical conductivity, dimensional stability, and/or excellent mechanical properties are desired. Typical uses for carbides and nitrides include semiconducting devices, automotive components, grinding and polishing applications, and as refractory in high temperature furnaces. These uses typically require a highly pure form of carbide in order to exhibit the desirable properties that carbides and nitrides are known for. Typical high purity carbide applications require a material that is greater than about 98% pure, while the commercial low grade carbides have purity levels between about 95% and 98%.
Another known use for carbides and nitrides is as blowing agents in foamed glass, ceramic or metal manufacturing processes. When carbide is used as a blowing agent, the carbons combine with oxygen under high temperature conditions to form CO and CO2 gases. The gases in turn are used to expand the softened glass, ceramic precursor or molten metal to form low-density foamed articles having a cellular structure. The same principle applies to the nitrogen in nitrides, which combines with oxygen to form one or more NOx gases that can be used to expand softened glass, ceramic or metal articles.
Despite the known utility of carbides and nitrides, their widespread use in glass and ceramic manufacturing has been limited to a large extent by their production cost. Even the technical grade products, which are generally less expensive than commercial grade products, are still costly when compared to conventional oxides such as silica and alumina used in the glass and ceramic industries. The high cost is attributable in part to the high cost of manufacturing.
It is also known that many composites containing silicon carbide are formed by dispersing pure silicon carbide particles, whiskers or fibers into a ceramic or glass forming material or metal (or metal alloy) and processing the mixture to form a composite. Homogeneous dispersion of silicon carbide in these composites is often problematic, requiring one or more processing steps to increase dispersion, yet still requires subsequent quality control checks. What is needed is a means of improving the dispersability of silicon carbide in glass, ceramic or metal composites.
From the foregoing, it will be appreciated that producing carbides and nitrides at a low cost and in a state that facilitates dispersability can have significant advantages in the glass, ceramic or metal composite industry where the carbides and nitrides are used extensively to improve the hardness, abrasion resistance, thermal stability or dimensional stability of such composites or where there are used as blowing agents to reduce the density of said composites. There is thus a need for an efficient process that significantly reduces the manufacturing costs of carbides and nitrides and provides them in a form that is amenable to further processing.